東西に分割した北太平洋指数の観点から見た総観気候学的特性

• Main Authors: 花戸, 佑輔, 山川, 修治
• Format: Report
• Language: Japanese
• Published: 日本大学文理学部自然科学研究所 2019
• Subjects: Aleutian Low; North Pacific Index (NPI); California Niño; blocking pattern; Pacific-North American (PNA) pattern; Pacific; aleutian low; Aleutian Islands
• Online Access: https://repository.nihon-u.ac.jp/xmlui/handle/11263/2363; https://doi.org/10.15006/chs20201054013

The Aleutian Low is a low pressure system which prevails over the Aleutian Islands mainly during the winter season. North Pacific Index (NPI） is known as an index of the strength of the Aleutian low (Trenberth and Hurrel,1994). This study examined the characteristics of the NPI, by which the subject area was divided into west sector and east sector, which was defined as ENPI and WNPI, respectively. Around the Hawaiian Islands, the amount of precipitation increased/decreased during the positive/negative WNPI phase. In the tropical eastern Pacific, sea surface temperature (SST） became lower/higher than an average in the positive/negative ENPI phase. Especially, significant positive anomalies were seen on the California coast in the negative ENPI phase. These characteristics are referred to as the California Niño (Yuan and Yamagata, 2014), which is considered to exert a considerable influence on the transportation of water vapor on the West coast of North America. In general, the Pacific-North American (PNA） pattern tends to develop in the positive/negative WNPI and ENPI phase, respectively. It was recognized that in the Northern hemisphere, a blocking pattern tends to be established when WNPI and ENPI are in the positive or negative phase.